Gas transportation modules (GTMs) are high pressure storage and transportation systems for compressed gases based on new alternative fuel cylinder designs. Initially used for compressed natural gas (CNG) in locations and countries where there was no infrastructure in place to move the gas from a central pipeline, refinery, or well, the usage of GTMs has increased to include a broader variety of gases, including helium, hydrogen, nitrogen, and breathing air.
Early GTMs
The first GTMs were typically “tube trailers,” constructed of bundles of steel cylinders (or tubes) mounted horizontally on a trailer or chassis, or in an ISO shipping container or frame. These systems, manufactured in the US by companies like Weldship Corp., FIBA, and Western Sales and Testing, continue to be in wide spread use today. Due to the weight of the steel and the corresponding highway weight limits imposed by the US Department of Transportation (USDOT), the capacity of these systems is restricted. More steel is required to contain increased pressure, so these systems quickly max out when they bump up against the over-the-road weight restrictions.
Underlying Technology
GTMs rely on bundles of high pressure cylinders “manifolded” together to a common fill/discharge load port(s). Since over 70 percent of the cost of these systems is in the cylinders, it is important to understand the underlying technology behind them. Driven to increase capacity, yet be lightweight, the technology grew from products that were initially used for stand-alone compressed gas storage; for SCBA (self-contained breathing apparatus) devices for fire fighters; for the storage of propellant for paint ball guns; and now for CNG-fueled fleet vehicles.
To understand the underlying technology of GTMs, it is important to know that there are basically four types of cylinders in use today.
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